This type of tender is endemic to Heligoland. Originally conceived as fishing boats they are used to ferry passengers from road-stead to shore. Judging from the visible kit, this one is used to work on lobster creels. https://pbase.com/wintermeer/image/135599378 shows its use in ferrying passengers. Being a part of local culture, the owners and sailors are organized it a guilt which puts its foot down whenever officials argue against this complicated m.o. Nowadays they grudgingly coexist with the express ferry from Hamburg and the ship serving Cuxhaven which has to provide access for the physically challenged, both enter the harbor proper and dock quayside.